SCOTT SIMON, HOST:
Dick Lugar, the longtime Indiana Senator, is fighting for his political life. Mr. Lugar faces a tough challenge in the Indiana Republican primary on Tuesday from the state's treasurer, who is running to his right. But at NPR's Tamara Keith reports, this isn't just a match between two candidates, it is a match between big-spending superPACs and other outside groups.
TAMARA KEITH, BYLINE: For six-term senator, Dick Lugar, yesterday brought the kind of news no candidate wants to hear, especially not at this point in a campaign. The Howey/DePauw Indiana Battleground Poll showed him down ten points to State Treasurer Richard Mourdock. Lugar held a press conference at his campaign headquarters in Indianapolis.
SENATOR DICK LUGAR: I'm just saying, positively register your vote, because if you do not, I may not be able to continue serving you.
KEITH: It's a remarkable reversal for a man who is an Indiana institution. This is the first time he's faced a primary challenge since he first ran for Senate in 1976. Brian Howey, publisher of the nonpartisan Howey Political Report, says six years ago, Lugar didn't even have a Democratic challenger in the general election.
BRIAN HOWEY: He hasn't really had any kind of political challenge at the ballot box since 2000. That's 12 years. I think the senator let his political organization kind of slide a little bit.
KEITH: And then in 2010, the political landscape shifted dramatically. The Supreme Court's Citizens United ruling and other legal decisions allowed unlimited fundraising and spending by independent groups. And spend they have in the Indiana's Senate race.
(SOUNDBITE OF POLITICAL AD)
UNKNOWN MAN #1: Citizen's United Political Victory Fund is responsible for the content of this advertising.
UNKNOWN MAN #2: Paid for and Authorized by Our Country Deserves Better PAC, Tea Party Express.
UNIDENTIFIED WOMAN: Club for Growth Action is responsible for the content of this advertising.
KEITH: It even got to the point where one superPAC ran TV ads complaining about another superPAC.
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UNIDENTIFIED MAN #3: Reject the negative Mourdock Club For Growth Alliance.
UNIDENTIFIED MAN #4: Paid for by Hoosiers for jobs.
KEITH: In total, outside groups, mostly superPACs, have spent more than four million dollars to sway the outcome of the race - that's more independent spending than in any other Senate race so far this year. And the majority of it supported the efforts of Richard Mourdock.
In the halls of the Capitol last week, Lugar seemed to yearn for a time without superPACs.
LUGAR: Well, the outside money is huge; Indiana seems to be the only playground and people are trying to prove their clout, but it's rather irrelevant to the issues of our campaign.
KEITH: Even though Lugar has raised and spent significantly more money, Richard Mourdock has been able to compete in part because several deep-pocketed groups are independently doing a whole lot to help him. Mourdock says he understood from the moment he launched his campaign that the rules had changed.
RICHARD MOURDOCK: We understood that there would be this superPAC involvement on both sides and we planned our budget, we planned our entire campaign strategy for it. And even though it's the first time such numbers have shown up in a federal race like this, a Senate race, it's not surprising.
KEITH: Mourdock is backed by most of the state's Tea Party groups, as well as national ones. And in many ways the race has become a proxy war between the GOP establishment and its right flank.
Brian Howey says for the far-right interest groups spending big, this race is a test of their might.
HOWEY: If Mourdock wins this primary and then wins in the fall, I think you're going to see this kind of sequence repeated in future election cycles all over the country.
KEITH: For his part, Mourdock says the fact that his campaign has gone from improbable to some think inevitable, is proof that conservative principles are winning in the fight for the soul of the Republican Party.
MOURDOCK: There are so many people who wanted to issue the obituary on the Tea Party movement. And I'll tell you what, the reports of the death have been greatly exaggerated, because they're not out waving the banners and standing under the don't tread on me flags now. But what they're doing is showing up to work for campaigns.
KEITH: Both campaigns have small armies of voters working this weekend, making phone calls and knocking on doors. That kind of passion for a candidate is something even unlimited the money can't buy.
Tamara Keith, NPR News.
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SIMON: And you're listening to NPR News.